The present invention relates to an ink jet system printer and, more particularly, to a printer head in an ink jet system printer of the ink on demand type.
Recently, an ink jet system printer of the ink on demand type has been practically developed, wherein ink droplets are emitted from a printer head at a desired time. In such an ink jet system printer of the ink on demand type, there is a problem that a nozzle orifice is blocked while the ink droplets are not emitted from the printer head for a considerably long period of time, or undesirable air bubbles are contained in an ink liquid disposed in the printer head. The orifice blocking problem is solved by providing an orifice cleaning system in the printer head. However, the air bubble problem is not solved yet.
The above-mentioned air bubbles are contained in the ink liquid disposed in the printer head due to, for example, the incomplete sealing of the printer head. When such air bubbles are contained in the ink liquid disposed in the printer head, the vibration energy supplied from a piezoelectric transducer attached to the pressure chamber is absorbed by the air bubbles. Thus, an accurate droplet formation is precluded.
Accordingly, an object of the present invention is to provide a novel printer head system which ensures an accurate droplet formation in an ink jet system printer of the ink on demand type.
Another object of the present invention is to provide an air bubble removing system for removing air bubbles contained in the ink liquid disposed in a printer head of an ink jet system printer of the ink on demand type.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, a preselected exciting signal is applied to a piezoelectric transducer attached to a pressure chamber in order to discharge air bubbles through an orifice portion. The exciting signal should have various frequencies and various voltage levels for removing various kinds of air bubbles contained in the ink liquid disposed in the pressure chamber.